The Inspector Morse spin-off show Lewis could be coming to an end, according to the original creator Colin Dexter.

The popular Oxford-set detective drama, which stars Kevin Whately as Inspector Robbie Lewis, has been broadcast on ITV1 since 2006.

But Dexter, 81, said: "I don't think he (Lewis) can go on much longer. They'll probably do one more series. The first two were ridiculously complex.

"They've got better. One reason (prequel) Endeavour did well is because everyone could understand it. People said to me, 'Brilliant. Typical Dexter'.

"Well, I didn't write it. I wish I had," he told the Radio Times. "The agreement is they won't put anything on telly without me seeing it. Sometimes we have to say it's not up to scratch."

Whately originally starred as sidekick to Chief Inspector Morse, played by the late John Thaw, in ITV1's Inspector Morse sleuth drama.

Dexter, who gave up alcohol because of "overconsumption", said of Thaw's grumpy alter-ego: "I'm usually asked why I killed him off - well, he died of natural causes: no exercise, diabetes, ulcers, and a bottle of Glenfiddich every day - which is not difficult."

The novelist added of his own drinking habits: "I didn't tell anyone I did that - not every day, but if I was writing in my study when everyone had gone to bed. I'm more imaginative on the wings of Bacchus.

"I was asked if I thought of an epitaph for him (Morse), and remembered 'Under this sod lies another'. Everyone clapped and thought what a clever chap I am, but my imagination is pretty feeble. I stole it from Spike Milligan."

Whately recently hinted that the drama, which also stars Laurence Fox and is about to return for a sixth series, might not last much longer, saying: "I'm now police retirement age this year, so the time is coming quite soon, I think."

Author Dexter also told the magazine he had a bleak prediction for the future.

"I don't see any hope for the human race. We're selfish and greedy, only interested in getting a few extra quid," he said.